Gas resources such as shale are accessed using a process called hydraulic fracturing. Fracturing, or “fracking,” process begins with the drilling of a well into a rock formation This technique further involves injecting a mixture of water, sand and a small amount of other additives (blend of chemicals) into a well. These fluids typically consist of about 90 percent water and 9.5 percent sand. Many of the ingredients in the remaining 0.5 percent of the mixture have common consumer applications in household products, detergents and cosmetics. These chemicals are used to reduce friction, prevent bacteria growth and protect the rock formation, making the hydraulic fracturing safer and more efficient.
The pressurized hydraulic fluid acts as a propping agent or proppant and creates hairline cracks in the shale and these cracks, held open by the sand particles, allow the gas to flow up through the wellbore to the surface. So, fracture sand is commonly introduced into the reservoir in an effort to create “conductive channels” from the reservoir rock into the wellbore, thereby allowing the hydrocarbons a much easier flow path into the tubing and up to the surface of the well.
Hydraulic fracturing is not new. It was first used in conventional oil and gas extraction in the late 1940s in North America. Since then, more than one million wells around the world have been drilled using hydraulic fracturing. In Alberta, it has been used for more than 60 years to safely and reliably fracture over 167,000 wells. What is new, however, is the use of multiple technologies in conjunction with one another to make accessing unconventional gas more feasible. By combining hydraulic fracturing with horizontal drilling, operators can safely produce affordable, reliable quantities of natural gas from shale and other unconventional sources.
The well equipment which is used to produce oil from a well typically includes components that are designed to separate the unwanted substances from the oil. For instance, a sand separator is commonly provided at the surface of the well to remove the sand that may be present as a result of fracking.
Conventional sand separation systems primarily rely on gravity to separate the sand from the fluids that are produced from a well. Typically, fluid is introduced into the central portion of a large, vertically oriented chamber through a pipe that is referred to as a stinger. The fluid flows slowly upward, typically through one or more baffles, to an outlet at the top of the chamber. The chamber has a large diameter so that the linear speed of the fluid flowing through the chamber will be minimized. This allows the sand to settle out of the fluid and fall to the bottom of the chamber, where it can be accumulated and removed.
There are various problems with the use of conventional sand separators to remove sand from oil or other fluids. For example, as noted above, the chamber of the apparatus needs to be large in order to minimize the speed of the fluid so that the sand can settle out. The large size of the apparatus can make it difficult to transport and install. Additionally, because of material cost, the sheer size of apparatus makes it more expensive.
Another problem is that it is difficult to accommodate the different operating conditions and fluid characteristics that may exist in different wells. For instance, one well may have a higher flow rate than another, so the settling of the sand out of the faster-flowing fluid may be less effective. Likewise, higher viscosity or lower temperature of the fluid may reduce settling in a conventional sand separator. Addressing these problems may require that an entirely different sand separator be used.
Overall, natural or manmade particulates can cause a multitude of producing problems for oil and gas operators. For example, in flowing wells abrasive particulates can “wash through” metals in piping creating leaks and potentially hazardous conditions. Particulates can also fill-up and stop-up surface flow lines, vessels, and tanks. In reservoirs whereby some type of artificial lift is required such as rod pumping, electric submersible pumps, progressive cavity, and other methods, production of particulates can reduce of the life of the down-hole assembly and increase maintenance cost.
It is an object of the present invention to obviate or mitigate the above disadvantages.